Routine use of supplemental oxygen does not improve survival in MI patients
The practice of giving oxygen to patients with MI is challenged by a recent registry-based randomized clinical trial showing that this widely accepted practice does not improve survival, according to results presented at the European Society of Cardiology Congress 2017 (ESC 2017) held in Barcelona, Spain.
The DETO2X-AMI study showed that in patients with suspected MI without hypoxaemia, giving supplemental oxygen at 6 litres per minute for a median of 11.6 hours (range 6–12 hours) through an open face mask did not reduce mortality rate within 1 year vs ambient air (5.0 vs 5.1 percent; hazard ratio [HR], 0.97; p=0.8). [N Engl J Med 2017, doi: 10.1056/NEJMoa1706222]
“The absence of an effect of supplemental oxygen on mortality was consistent in all subgroups, such as in patients who were smokers or nonsmokers, and patients with or without diabetes, chronic kidney disease, previous MI or previous percutaneous coronary intervention procedures, regardless of baseline characteristics or final diagnosis,” said investigator Dr Robin Hoffman of the Karolinska Institutet, Stockholm, Sweden.
There was also no significant difference between the two groups in terms of cumulative troponin T concentration (oxygen group 946.5 ng/L vs ambient air group 983 ng/mL; p=0.97).
“ESC guidelines have gradually shifted towards more restrictive use of oxygen. While the current recommendations were based on expert opinion only, we can now add substantial data from this clinical trial,” said investigator Professor Stefan James of the Uppsala University, Uppsala, Sweden.
The registry-based nationwide randomized clinical trial, with 69 participating Swedish centres, included 6,229 predominantly male patients (70 percent) with classical acute MI symptoms for less than 6 hours. The patients had a median age of 68 years (range, 59-76 years), oxygen saturation of ≥90 percent, and presence of ischaemic ECG changes and troponin elevation.
Data analysis was done through the Swedish population registry and SWEDEHEART, the country’s online cardiac registry.
“The population recruited for the study is at least six times larger than populations of similar studies done in previous years,” Hoffman pointed out.
“This form of clinical trial is cost-effective and efficient, representative of real-world practice, able to recruit patients with ease, and ideal for testing ‘established’ treatments… The major implication is that registry-based randomized clinical trials may become the new gold standard for routine clinical implementation,” discussant Dr David Newby of the University of Edinburgh, Scotland, commented.
Oxygen therapy has been used for more than a century and is widely recommended by guidelines including those of the ESC, the rationale being that increased oxygen delivery to the ischaemic myocardium reduces infarct size and subsequent complications such as heart failure or arrhythmias. [Eur Heart J 2016; 37:267-315; Eur Heart J 2012; 33: 2569-2619]